The level of hardness in water can have a deleterious effect in many systems. For example, when hard water is used in conjunction with cleaning compositions, hard water can cause precipitation of hard water scale or components of a cleaning agent. In general, hard water refers to water having a level of calcium and magnesium ions in excess of about 100 ppm expressed in units of ppm calcium carbonate. Often, the molar ratio of calcium to magnesium in hard water is about 2:1 or about 3:1. Although most locations have hard water, water hardness tends to vary from one location to another.
Etching or corrosion of glass, porcelain and ceramic due to water hardness is a common problem in warewashing and surface cleaning. Water hardness can be addressed in a number of ways. For example, the water can be softened by replacing the calcium and the magnesium present in the water with sodium. The warewashing composition can also include builders or chelating agents at levels sufficient to handle the water hardness. Water softeners, however, break down on occasion or run out of material that provides the softening effect. In addition, certain environments may provide water having a hardness that exceeds the builder or chelating capacity of the warewashing detergent composition. As a result, free calcium ions may be available to attack active components of the composition, to cause corrosion or precipitation, or other deleterious affects. Accordingly, conventional cleaning compositions include additional ingredients to combat corrosion or etch.
It is entirely unexpected that a hardness ion would have a beneficial effect on reducing etching and/or corrosion of glass.